Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis – Ligament or tendon
Reexamination Certificate
2001-06-14
2003-05-13
Philogene, Pedro (Department: 3732)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Implantable prosthesis
Ligament or tendon
C606S075000, C606S232000
Reexamination Certificate
active
06562071
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
Embodiments of the present invention are related to orthopaedic surgical devices, such as implants, and procedures using the implants. More particularly, embodiments of the present invention are directed to surgical devices involved in replacing, reconstructing or securing synthetic or biological connective tissue to a bone surface, such as, for example, attaching and maintaining a replacement anterior cruciate ligament (ACL) against a bone.
Embodiments of the present invention particularly relate to surgical implants manufactured of biocompatible (permanent or bioabsorbable) material, e.g., plastic, metal, or bioabsorbable (or biodegradable) polymer, copolymer, polymer alloy or composite and which implants are used for fixation of a synthetic or biological (connective tissue) graft into a drill-hole in a bone. Grafts according to the present invention include natural (auto- or allograft) and/or synthetic substitutes to ligament or tendon. Synthetic implants according to the present invention may be ceramic and/or polymeric and include fibrous braid implants or other implants comprised of fabric.
2. Description of Related Art
Reconstruction is the standard of care after anterior cruciate ligament (ACL) injury. In surgery it is generally known to use an autograft taken e.g., from the knee of the patient, to replace the ruptured ACL. The two most commonly used are the bone-patellar tendon bone (BPTB) and the hamstring tendon (semitendinosus tendon with or without gracilis tendon), although allografts, synthetic grafts and quadriceps tendon grafts have also been used as ACL substitutes. The surgical techniques of the ACL reconstruction using bone-tendon bone (BTB) graft and hamstring tendon graft are described in detail in the following references: Beck, C. L., Jr.; Paulos, L. E.; Rosenberg, T. D.: “Anterior cruciate ligament reconstruction with the endoscopic technique,”
Operative Techniques in Orthopaedics,
2:96-98, 1992; Stähelin, A. C.; Weiler, A.: “All-inside anterior cruciate ligament reconstruction using semitendinosus tendon and soft threaded biodegradable interference screw fixation,”
Arthroscopy,
13:773-779, 1997; Fu, F. H.; Ma, C. B.: Anterior Cruciate Ligament Reconstruction Using Quadruple Hamstring.
Operative Techniques in Orthopaedics,
9:264-272, 1999. Additional references of interest include Hoffman, R. F. G.; Peine, R; Bail, H. J.; Sudkamp, N. P.; Weiler, A.: “Initial fixation strength of modified patellar tendon grafts for anatomic fixation in anterior cruciate ligament reconstruction,”
Arthroscopy,
15:392-399, 1999.
In brief, the ruptured ACL is removed and drill-holes are made into the distal femur and proximal tibia into or into close vicinity of the original insertion sites of the ACL. The replacement substitute (graft) is harvested either from the patellar tendon (BTB) or from the semitendinosus- and gracilis muscle tendons (hamstring graft), pulled through the drill-holes to replace the ruptured ACL and finally fixed into these drill-holes, leaving the tendon part to act as a new ACL.
Rigid fixation of the ACL graft has been recognized as one of the most important factors that determine the long-term success of an ACL reconstruction (Kurosaka, M; Yoshiya, S; Andrish, J T: “A biomechanical comparison of techniques of graft fixation in anterior cruciate ligament reconstruction,
Am. J. Sports Med.,
15:225-229, 1987; Brand, J., Weiler, A., Caborn, D. N. M., Brown, C. H. Johnson, D. L.: “Current Concepts: Graft Fixation in Cruciate Ligament Reconstruction.”
Am. J. Sports Med.
28: 761-774, 2000). Further, the tibial fixation of hamstring tendon grafts is considered more problematic than femoral fixation (Larson, R.: “Fixation techniques for hamstring and other soft tissue ACL grafts. The science: Comparative laboratory and clinical studies,”
Proceedings of the Specialty Day,
the American Orthopaedic Society for Sports Medicine p. 99-102, Orlando, Fla., Mar. 18, 2000; Brand, J., Weiler, A., Caborn, D. N. M., Brown, C. H. Johnson, D. L.: “Current Concepts: Graft Fixation in Cruciate Ligament Reconstruction.”
Am. J. Sports Med.
28: 761-774, 2000), mainly because the forces are subjected to the ACL substitute (graft) parallel with the tibial bone tunnel and the bone quality is substantially inferior in the tibia than in the femur.
Among the currently available soft tissue (hamstring) graft fixation implants, interference technique, in which the so called interference screw is inserted into the space between the drill-hole and the end of the graft to lock the graft into the drill-hole, is currently the most commonly used method to secure an ACL substitute to a bony drill-hole in an ACL reconstruction. The fixation screws, like interference screws, are normally made of metal, like stainless steel or titanium or of a bioabsorbable polymer, like polylactide. Metallic and/or bioabsorbable polymeric materials and composites suitable for manufacturing of fixation screws, are described in the literature (Vainionp{umlaut over (aa)}, S.; Rokkanen, P.; Törmälä, P.: “Surgical Applications of Biodegradable Polymers in Human Tissues.”
Progr. Polym. Sci.,
14:679-716, 1989; Weiler, A.; Hoffman, R. F. G.; Stahelin, A. C.; Helling, H. J.; Sudkamp, N. P.: Biodegradable Implants in Sports Medicine: The Biological Base. Current Concepts
Arthroscopy
16:305-321, 2000).
During interference screw insertion, technical complications such as the threads of the screw damaging the graft or passing sutures, the graft rotating with the screw so that the optimal position of the graft is lost and/or the graft is damaged or the screw becomes inserted non parallel (divergent) to the graft thereby significantly decreasing the strength of fixation, often occur. There are also concerns specific to the metal interference screws. For example, in case of a need for revision surgery, metal screws can significantly complicate the operation, as the hardware inserted in the primary reconstruction has to be removed, sometimes resulting in considerable loss of bone in the fixation site, and thus, decreasing the strength of the fixation of the revised graft. In most severe cases, it may even be necessary to perform bone grafting prior to revision surgery (Brown, C. H.; Steiner, M. E.; Carson, E. W.: “The uses of hamstring tendons for anterior cruciate ligament reconstruction: Technique and results,”
Clin. Sports Med.,
12:723-756, 1993; Schroeder, F. J.: “Reduction of femoral interference screw divergence during endoscopic anterior cruciate ligament reconstruction,”
Arthroscopy,
15:41-48, 1999). Metal screws have also been shown to disturb postoperative MRI evaluation (Shellock, F. G.; Mink, J. H.; Curtin, S.; Friedman, M. J.: “MR imaging and metallic implants for anterior cruciate ligament reconstruction: assessment of ferromagnetism and artifact,”
J. Magn. Reson. Imaging,
2:225-228, 1992). The problems specific to metal screws can naturally be avoided by the use of screws made of bioabsorbable materials, but other problems arise, such as the bioabsorbable screw breaking during screw insertion. Also, the drill-hole has to be threaded for the insertion of the bioabsorbable screw, which not only delays surgical operation, but also increases trauma and removes mechanically stronger cortical bone, thus reducing the grip of the screw into the bone. Complications associated with the surgical technique, like those listed above, are also provided in the literature (Bach, B. R.: “Arthroscopy-assisted patellar tendon substitution for anterior cruciate ligament insufficiency,”
Am. J. Knee Surg.,
2:3-20, 1989; Barber, A. F.; Buxton, E. F.; McGuire, D. A.; Paulos, L. E.: “Preliminary results of an absorbable interference screw,”
Arthroscopy,
11:537-548, 1995; Matthews, L. S.; Soffer, S. R.: “Pitfalls in the use of interference screws for anterior cruciate ligament reconstruction: Brief report,”
Arthroscopy,
5:225-226, 1989; Matthews, L. S.; Lawrence, S. J.; Yahilo, M. A.; Sinclair, M. R.: “Fixation strength of patellar tendon-bone grafts,”
Banner & Witcoff , Ltd.
Philogene Pedro
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